minaton.c

/*
  Copyright 2015 Nick Bailey
*/

#include <math.h>
#include <stdlib.h>
#include <string.h>

#include "lv2/lv2plug.in/ns/lv2core/lv2.h"

#define minaton_URI "http://nickbailey.co.nr/plugins/minaton"

typedef enum {
	minaton_GAIN   = 0,
	minaton_INPUT  = 1,
	minaton_OUTPUT = 2
} PortIndex;

typedef struct {
	float* gain;
	float* input;
	float* output;
} minaton;

static LV2_Handle
instantiate(const LV2_Descriptor*     descriptor,
            double                    rate,
            const char*               bundle_path,
            const LV2_Feature* const* features)
{
	minaton* self = (minaton*)malloc(sizeof(minaton));

	return (LV2_Handle)self;
}

/** Connect a port to a buffer (audio thread, must be RT safe). */
static void
connect_port(LV2_Handle instance,
             uint32_t   port,
             void*      data)
{
	minaton* self = (minaton*)instance;

	switch ((PortIndex)port) {
	case minaton_GAIN:
		self->gain = (float*)data;
		break;
	case minaton_INPUT:
		self->input = (float*)data;
		break;
	case minaton_OUTPUT:
		self->output = (float*)data;
		break;
	}
}

/** Initialise and prepare the plugin instance for running. */
static void
activate(LV2_Handle instance)
{
	/* Nothing to do here in this trivial mostly stateless plugin. */
}

#define DB_CO(g) ((g) > -90.0f ? powf(10.0f, (g) * 0.05f) : 0.0f)

/** Process a block of audio (audio thread, must be RT safe). */
static void
run(LV2_Handle instance, uint32_t n_samples)
{
	minaton* self = (minaton*)instance;

	const float        gain   = *(self->gain);
	const float* const input  = self->input;
	float* const       output = self->output;

	const float coef = DB_CO(gain);

	for (uint32_t pos = 0; pos < n_samples; pos++) {
		output[pos] = input[pos] * coef;
	}
}

/** Finish running (counterpart to activate()). */
static void
deactivate(LV2_Handle instance)
{
	/* Nothing to do here in this trivial mostly stateless plugin. */
}

/** Destroy a plugin instance (counterpart to instantiate()). */
static void
cleanup(LV2_Handle instance)
{
	free(instance);
}

/** Return extension data provided by the plugin. */
static const void*
extension_data(const char* uri)
{
	return NULL;  /* This plugin has no extension data. */
}

/** The LV2_Descriptor for this plugin. */
static const LV2_Descriptor descriptor = {
	minaton_URI,
	instantiate,
	connect_port,
	activate,
	run,
	deactivate,
	cleanup,
	extension_data
};

/** Entry point, the host will call this function to access descriptors. */
LV2_SYMBOL_EXPORT
const LV2_Descriptor*
lv2_descriptor(uint32_t index)
{
	switch (index) {
	case 0:
		return &descriptor;
	default:
		return NULL;
	}
}